Press brakes of the type used for forming plate, sheet, and other forms of metallic stock typically have upper and lower die sets which are clamped to the bed and ram of the press brake, respectively. Usually the upper and lower dies are configured so that the clamping system retains the dies from any undesirable excessive movement during operation of the press brake. An example of such a clamping system is shown in U.S. Pat. No. 4,787,237 to David L. Huston et al dated Nov. 29, 1988. The clamping system of this patent utilizes a pair of upper and lower jaws which are engaged with the connecting portion of the upper and lower dies, respectively. Since the upper and lower dies have a relatively narrow configuration in transverse cross-section the clamping force supplied to the jaws is may be adequate to prevent tipping movement of either of the upper and lower dies.
Upper and lower dies often vary in configuration depending upon the nature of the forming work to be done. In some applications the dies are large relative to the transverse cross-sectional thickness of the clamping portion of the ram and bed and in other applications the dies are offset relative to the transverse cross-section of the clamping portion of the ram and bed. In applications where the connection of the die to the press brake is transversely offset relative to load applying end of the die uneven loading occurs which frequently results in failure of the die. In applications where the dies are very large and the work to be formed is relatively thick, several tons of offset die loading may be applied which will result in cocking, bending and/or braking of the die at the connecting portion of the die to the press brake due to the relatively narrow cross-sectional thickness of the clamping portion.
In the applications where the load applying end of the die, the end which is engageable with the material being formed, is transversely offset from the connecting portion of the die at the connection to the press brake, uneven distribution of loading occurs. This uneven loading may cause the clamping system to fail which can cause damage to the brake press, the material being formed. Further, offset loading of the system which clamps the die to the press brake may cause premature wear which will affect the accuracy of operation and result in excessive scrap and rework.
Failure of either the die or clamping mechanism caused by the unequal distribution of loading of the die will result in undesirable down time of the brake press which can disable the manufacturing operation in which the brake press is utilized, costing the manufacture in productivity and cash receipts.
Since the cross-sectional transverse thickness of the clamping system is often relatively small in comparison to the size of the die being supported and the magnitude of the load being applied, any transverse offset of the die which will cause uneven loading of the die (tipping loads) will place undesirable loads on the clamping system and result in failure of the connecting system and the press brake.
Over time forming dies tend to wear away which causes the connection to the press brake to become sloppy. Such wear usually results in poor stock forming accuracy. Also, the sloppy fit accelerates further wear and causes premature failure of the die. In order to correct the problem the die is usually scrapped or when possible repaired. In either case there is substantial cost involved. Because of the cost of replacement or repair the problem is often neglected which ultimately results in failure of the connecting system, die and associated componentry. Should the wear become excessive, clamping of the die in position so that travel of the die longitudinally of the ram or bed will be impossible. Thus, the die will wander longitudinally during the forming operation and require frequent adjustment. Should the adjustment not be done, scrap parts will be generated.
The present invention is directed to overcoming one or more of the problems as set forth above.